This invention relates generally to excavating and construction equipment, and more specifically to attachments for backhoe equipment.
In the construction and excavation industry, many kinds of equipment have been developed to assist the workers in their numerous tasks. One piece of equipment that has achieved nearly universal acceptance in the industry is the wheel or track-mounted tractor equipped with a hydraulic backhoe and bucket. These machines can perform a variety of jobs, including lifting, trenching, clearing and excavation.
Some construction jobs, however, require a backhoe tool that can grip or clamp material from both sides, rather than just move or "scoop" the material from one side. For example, the picking up and placement of logs or pipe is best accomplished with a tool that provides a clamping effort.
Several types of backhoe attachments have been designed to achieve this clamping effect. Typically, the standard backhoe bucket is replaced with a completely self-contained clamping system including a pair of "jaws" each actuated by its own hydraulic cylinder. Alternatively, a second hydraulically actuated jaw can be added on to an existing single bucket system. Such systems do indeed achieve the required clamping effect, but they are very costly in that they require a second hydraulic unit, and often render the original backhoe equipment unsuitable for standard trenching-type operations. In addition, these attachments are often heavy and difficult to use, as well as highly vulnerable to damage.
Some backhoe attachment units have been developed which utilize a "stiff arm" portion which provides a fixed second jaw against which the movable backhoe bucket can clamp an object. However, these systems generally are limited in their range of motion, and hence have reduced application.
Of late, backhoe clamping attachments have been provided which can be easily added on to standard existing backhoe equipment. This type of clamping attachment mounts directly to the linkage and pivot points of a standard backhoe dipper and bucket, and converts the bucket to a clamping system by using the existing backhoe leverage to actuate a clamping jaw. Although these clamping devices require few parts, resulting in a product that is easy to manufacture, compact to ship and low in cost, these clamping attachments are inadequate in the respect that the bucket cannot "curl" all the way into the dipper arm, as if the clamping attachment were not attached to the backhoe. Also, these clamping attachments require the use of a removable "kidney link" and four removable pins to hold the kidney link to the backhoe. Frequently, the kidney link and pins which hold the kidney link to the backhoe are misplaced or lost.
FIGS. 1 and 2 present views of a prior art clamping device, over which the clamping device of the present invention is an improvement. Thus, FIG. 1 is a perspective view illustrating a prior backhoe clamping device 10 as mounted to a standard backhoe dipper and bucket arrangement. The clamping device includes right and left mounting brackets 12a, b (left mounting bracket 12b cannot be seen from this perspective), right and left link/bracket pins 14a, b (left link/bracket pin 14b cannot be seen from this perspective), right and left clamp link 16a, b, right and left clamp link pins 18 a, b, and right and left clamp arms 20a, b. In this conventional arrangement, clamp arms 20a, b are secured to each other by a plate 22, and to the dipper and bucket arrangement by a clamp/dipper pin 24. The disadvantages of this arrangement will become apparent when the inventive clamping device is described below. Gripping protrusions or teeth 25 on the clamp arms improve the clamping ability, and are a standard item.
The pertinent parts of the original backhoe dipper and bucket arrangement include a dipper arm 30, a lower side bucket link pin 32, right and left side bucket links 34a, b, and upper side bucket link pin 36, a hydraulic cylinder shaft 38, a bucket linkage 40, a bucket linkage/bucket pin 42, and a bucket 44.
In a prior method of attaching the clamping device, right and left mounting brackets 12a, b are first welded or otherwise secured to the outside surfaces of the right and left side bucket links 34a, b, respectively. When welding these mounting brackets 12a, b, proper placement of the mounting brackets is critical, for it is from the offset pivot effect to the clamp link 16a, b that the backhoe clamping device gets its desired results. It is preferable to locate the brackets to maximize the resultant clamp leverage with the available amount of stroke. Thus, one must place the pivot point of the link/bracket pins 14a, b below and to the side of the center of the bucket of the side bucket links 34a, b, the movement of the bucket links generating several times the clamping force at the clamp arms than would be generated by a pivot point placed in the center of links 34a, b. Once this mounting bracket is properly positioned and welded into place, the rest of the backhoe clamping device is then assembled.
FIG. 2 shows the prior clamping device in its stored position. To store the clamping device, the link/bracket pins 14a, b, clamp links 16a, b and clamp/link pins 18 a, b must be removed to enable the clamp arms 20a, b to be raised back until plate 22 contacts dipper arm 30. A chain 28, which is secured to plate 22, is then attached to a grab hook 31, which is welded to the dipper arm 30.
As can be seen with reference to FIGS. 1 and 2, this arrangement of the clamping device presents certain disadvantages: welding of the mounting brackets 12a, b requires experience to know exactly where to mount the brackets to bucket links 34a, b; pins 14a, b, 18 a, b are completely removed, along with clamp links 16a, b, to be put somewhere such as a tool box, which may become separated from the backhoe; and when the clamping device is in its stored position as shown in FIG. 2, the bucket cannot curl to its full curl position (i.e., the bucket cannot travel to a full closed arc position without interference between the dipper arm and the clamp arm).
It would be advantageous to design a clamping device which is easily and quickly attached to a backhoe, in which the clamp link and associated pins remain attached to the backhoe in both a stored and operable condition. It would further be advantageous if the original bucket would have its full curl.